Abstract Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), is one of the oldest known human maladies. Yet this disease is still one of the major causes of mortality, as almost 2 million people die each year from TB. Despite the widespread use of an attenuated live vaccine and several antibiotics, there is more TB than ever before, requiring new vaccines, drugs and more specific and rapid diagnostics. Mtb is a facultative intracellular pathogen that replicates in macrophages and extracellularly in lung cavities. During infection, Mtb is exposed to different environments and stress conditions to which it must adapt in order to survive and multiply. Iron deficiency is one of those conditions. As is the case for most living organisms, Mtb requires iron as cofactor for enzymes that are involved in essential functions, including respiration, DNA replication and defense against toxic oxidative stress. Thus, if ways can be found to interfere with Mtb's ability to acquire iron, these information could be useful in designing new anti-tubercular therapies. The specific aims of the proposal are first, to understand how the major pathway of Mtb iron acquisition, using siderophores, functions. This includes learning how iron complexed to siderophores is imported into Mtb and how the iron is then released in a form that can be used by the cell for its essential functions. The mechanism of siderophore secretion will also be part of this aim, as will a characterization of heme uptake a non-siderophore mediated pathway of Mtb iron acquisition. The second aim seeks to understand why IdeR, the major regulator of iron uptake and storage is essential, using a combination of in vitro and in vivo approaches. The third aim will use the information obtained in the first two aims and earlier work to develop new live, attenuated safe vaccine candidate strains that could be used to prevent TB in the general population, as well as immunocompromised individuals.